Battered, bruised and angry, four of the Britons arrested in Genoa during the anti-capitalist demonstrations arrived home yesterday claiming they had been beaten and tortured by baton-wielding Italian police.

They alleged they had been held in bare concrete cells, given little or no food and ordered to stand spread-eagled for up to two hours. Throughout, they were denied access to lawyers or consular staff.

A fifth protester who is still too badly injured to return described in vivid detail the horrific beatings he received as he tried to flee the police.

The government has asked the British ambassador to investigate the allegations but has so far stopped short of condemning the Italian police, to the anger of the protesters and human rights campaigners.

In Genoa there is growing concern about the actions of the police after one officer told a newspaper they had attacked peaceful protesters in revenge for earlier violence, sung fascist songs and threatened women with rape.

The four who returned, Daniel McQuillan, 35, Jonathan Blair, 38, Richard Moth, 32, and Nicola Doherty, 27, were among the 93 arrested on Saturday night when police burst into a school being used by an umbrella organisation, the Genoa Social Forum, to help co-ordinate the G8 summit protests.

Prosecutors, who claimed Molotov cocktails were found in the building, said they could face charges ranging from conspiracy to possessing explosives. But when they were brought before a magistrate on Wednesday they were questioned only briefly then released.

The four, looking tired, pale and angry, were met by relatives and friends when they touched down at Heathrow.

In a statement they compared the room they were first held in to a "field hospital in the Crimean war". It read: "Most of those present required hospital treatment. Several were carried out on stretchers. People suffered broken bones and head injuries and many were covered in blood."

Mr McQuillan, a computer consultant for a charity and the son of a former honorary physician to the Queen, showed his blood-spattered shirt, which he said he had been forced to wear for four days.

Speaking of the raid, which was carried out as protesters slept, he said: "It was terrible, we could hear the screaming and beating going on." He said one police officer struck him on the head with a baton: "I rolled on to the floor on my left side and they continued beating us."

He suffered arm, leg and head injuries. While strapped to a trolley in hospital, his money and passport were confiscated. He was then moved to a holding cell. "We were in a large room in whatever clothes we were wearing and nothing else, no sleeping bags, no food for about 36 hours. It was something like a Chilean prison."

A fifth Briton is still in hospital in Genoa. Mark Covell, a web designer for the Genoa protesters' IndyMedia site, told how he and a friend had heard the police coming and tried to escape from the school. He sensed rather than saw an estimated 300 riot police sprinting towards him from both ends of the street.

"A carabinieri whacked me in the neck and with his shield pushed me against the wall," he said. "I fell to the ground and four or five carabinieri started kicking me, really hard, in the chest, legs, back.

"I had my arms up, saying 'don't hit me, I'm not resisting arrest'. I could say it only in English so I suppose they couldn't understand that. There was this extraordinary sound as they beat their shields and charged."

Then he was beaten for a second time. "I heard my ribs break, like snapping matchsticks. I was still conscious at this stage. They take a running jump at you like kicking a football." Somebody dragged him by the neck to the front of the school and he was beaten again. "That was by far the worst. I thought, my God, this is it, I'm going to die."

He tried to remain lying on his right side. He said: "I knew if I turned over I would die. And I thought that if I could just keep one eye open I would stay alive."

He lost consciousness and woke up in the San Martino hospital. He had five broken ribs, some of which pierced his lung and possibly a ruptured spleen. He has not been able to stand up since and lost 10 teeth.

The police had wanted him moved to the military wing of the hospital but doctors dissuaded them. Mr Covell said: "I want the carabinieri charged with attempted murder. I didn't mind their beating me the first time but the second and third time they tried to kill me."

Some protesters have criticised the British government for not doing enough to make sure they were safe and for failing to condemn the Italian authorities.

The foreign secretary, Jack Straw, said he had received assurances from the Italian government that the allegations of police malpractice would be properly inves tigated.

"We have spoken to the Italian administration at the highest level and they have agreed that these allegations will be fully investigated as part of the wider investigation into police malpractice by the Genoa public prosecutor," he told reporters in London.

"We have made it clear to the representatives of those who are making these allegations if we receive details we will make sure they are received by the Italian government and properly dealt with. The Italians have shown consistently that they live by the rule of law. They have given these undertakings and we expect them to abide by them."

The foreign office said it had asked Britain's ambassador Sir John Shepherd to seek an urgent meeting with Italy's foreign minister, Renato Ruggiero, to ask for the allegations to be fully investigated. But a spokeswoman also re-emphasised Tony Blair's comments made at the weekend about the difficulty of policing such demonstrations.

The Liberal Democrat foreign affairs spokesman, Menzies Campbell, said: "The Foreign Office must make the strongest possible representations to the Italian government. The people who have returned give all the appearance of having been subjected to pretty brutal treatment."

Mr Campbell also expressed concern that the four who returned had not been allowed to see consular staff or lawyers until Wednesday.

Stephen Jakobi, of Fair Trials Abroad, said the lack of consular access was "barbaric" and called on the European Union to examine whether the Italian authorities had contravened the Vienna Convention.

Amnesty International is monitoring the Italian authorities' actions and will demand an independent commission of inquiry if it feels that their investigations prove unsatisfactory.

In Italy there is mounting consternation at how the Britons were treated, espe cially following the "confession" of one unnamed officer in the newspaper La Repubblica.

He said: "They [the police] lined them up against the wall. They urinated on one person. They beat people up if they didn't sing Facetta Nera [a fascist song]. One girl was vomiting blood but the chief of the squad just looked on. They threatened to rape girls with their batons."

Francisco Martone, a Green party senator representing the Genoa constituency, told BBC Radio 4's World at One pro gramme: "We do think this behaviour has no place in a democratic society, so this is why we are going to ask formally to the government to explain the behaviour and to have an investigation into these facts."

The four, who have been banned from Italy for five years, are expected to join a picket outside the Italian embassy in London on Saturday.